1. Field of the Invention
The present invention relates to a control system for an internal combustion engine wherein the torque developed by the engine is detected to automatically control th ignition timing of the engine toward attaining the optimum value and thereby to accomplish an improved engine efficiency as well as an improved fuel economy.
2. Description of the Prior Art
In the past, the ignition timing of an Otto-cycle internal combustion engine has been controlled according to a so-called program control wherein a spark advance pattern is preset using principally the number of revolutions and the boost pressure of the engine as controlling parameters and the pattern is followed faithfully. A disadvantage of this type of ignition timing control is that the optimum ignition timing for obtaining the maximum engine efficiency or the minimum fuel consumption rate cannot be programmed by using only two controlling parameters, i.e., the number of revolutions and the boost pressure of the engine and therefore one must be content with a relatively simple spark advance pattern in consideration of such limiting factors as the productivity and manufacturing cost of the required control system.
Another disadvantage of the conventional program control type ignition systems is that apart from the problem of incompleteness of such programmed pattern, these systems cannot overcome other problems such as the occurrence of errors due to the variations in characteristics among similar related units, e.g., engines and ignition systems, adjustment errors and the problem of change of characteristics with time caused by increased service time.